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Overhaul of electrical system

We live on our narrowboat and need to completely overhaul our electrical system including batteries. We use approx 85 -90amps per day ( Winter use). If you had to do this job what would you fit? We have Adverc battery management system and a galvanic isolater but little else. What are your thoughts on generators - either inboard or portable? We know that this will all come at a price but want to keep it at a sensible level. Many thanks

Asked by: Sharron Watson  | 10.05pm, Saturday 26 February


WW says:

The big question comes down to- will you be cruising every (or most) days- or will you be tied up?
If you are tied up, will you have access to a 230V mains supply?
If your daily consumption is around the 90Ah level, does this include washing machines, etc?
If you are cruising, then a battery bank of, say 300Ah as a minimum, would be a very good starting point- with the engine alternator of 50amps plus being able to recharge them through the Adverc system within a 3 to 4 hours period. A reasonable sine wave inverter would provide you with the 230V power you require- the actual size dependant on the load you want to apply (washing machines being the highest load, and requiring the best quality frequency stabilisation).
If you have twin alternators, it might be worth using the smaller alternator to charge the starter battery and a (say) 200Ah battery bank for the fridge (and central heating, if fitted), with the larger alternator charging a 300Ah bank, which would power the rest of the domestics and the inverter.
If you are tied up, with a 230V supply, then a good quality 4-stage battery charger for the main battery bank (and second bank, if needed), plus a low-level trickle charger for the starter battery. The main charger should be around 10% of the capacity of the battery bank- so a 300Ah bank would need around a 30A charger, though this is only a rough guide.
If you are staying fairly immobile, with no mains supply, then a fixed diesel generator, powering a good 50A+ mains charger, would be ideal- but certainly not a cheap option! An encapsulated 3KW generator would be the quietest, though at the £3,500 plus range (not including fitting), you would be have to be sure it was for you!
Portable generators can be useful for occasional use, but their buzzing can be a nusiance. A quieter, inverter-based portable (like the ubiquitous Honda geneartors) are quiet and portable. HOWEVER, as they are petrol powered, they need to be stored in their own self-draining locker, both for safety and the BSS (like a gas locker- but NOT in your existing gas locker) plus the petrol would need to be stored in a similar fashion. Any leakage of petrol vapour (which happens with changes in temperature, not just with "leaks") could be potentially disasterous.
A portable generator needs to be run on the bank, not on the boat- and properly earthed through the earth lead on the generator (something most boat owners never do, which is quite daft!)- a length of wire to a mooring spike works fine! The generator will easily power a large charger, as well as 230V appliances up to the limit of the generator. Bear in mind that inductive loads (like anything with a motor) might require a start-up current larger than the output of the generator.
A portable diesel generator is usually quite heavy, and difficult to shift, though the problems with storing fuel and positioning the generator are far easier. For the price of most portable diesel generators, a little more would get one to fit.
If you want anything else, just shout!
Mark

Mark Langley  | 10.04AM, Monday 28 February

Typo... should have been £5,500!
However, you might be able to find a DC only diesel generator for a fraction of the price... or, pushing it, you could install and make your own, using, say a 4hp/1-cylinder diesel engine from a dump druck or water pump, and link to a 110Ah alternator! Could be done at a reasonable cost, and you could make your own enclosure. If you have a trad engine room, then you might be able to squeeze one in! You could duct the exhaust through the hull and feed in air from either the roof or the engine space. An air cooled unit might be noisier, but probably less so than running your vintage engine off-load. Even a Lister ST1 can be made quite quiet with prober sound insulation!

Mark Langley  | 1.34PM, Monday 28 February

Should have added- you could have a fitted petrol generator inboard, but run it from LPG, which would be cheaper, but opens up another raft of issues!

Mark Langley  | 1.36PM, Monday 28 February


Readers say:

Thanks for your very comprehensive reply Mark. I did forget to mention one thing - we have a vintage engine! This is the main reason why we're thinking of having a gennie fitted as we really don't want to run it just to charge the batteries. It's lovely to cruise with but when stationary and just charging the batteries it's very noisy, then of course you have to add in the slow revving etc and the whole thing becomes a bit of a headache. I think considering what you have said an inboard gennie would be the answer. I'd like to know where you can get one for £3,500 though as I can only find more expensive ones! LOL!

Sharron Watson  | 12.36PM, Monday 28 February

A typo! Thought it might be as I've looked into inboard gennies and they are quite pricey. However we might look into the suggestions you've put forward as they look quite interesting. We don't have a traditional engine room as our boat was built as a residential boat and the trad engine is enclosed where the boatman's cabin would be. We do have quite a bit of room though so we're going to look into your suggestions.Thanks again Mike. Something else for us to think about!

Sharron Watson  | 6.31PM, Tuesday 1 March

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